John Hewson is a Principal Member of the Technical Staff in the Engineering Sciences Center at Sandia National Laboratories. There he heads the physics model development for the reacting flow modeling and multiphase flow modeling capabilities. Prior to joining the Engineering Sciences Center, John spent time at Sandia's Combustion Research Facility and Lawrence Berkeley Laboratory. He received his Ph.D. from the University of Californnia San Diego and his B. S. from the University of California, Berkeley.